Optical disk, an optical disk device, and a method of managing defects in an optical disk

ABSTRACT

When optical disk defects are managed by using non-defective areas in place of defective areas, different criteria are used for detecting the defects, depending on the type of data recorded on the disk. For example, to avoid interruptions of real-time recording, less strict criteria are used when audio or video data is recorded than when computer data is recorded. The criteria themselves may also be recorded on the disk.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method of managing defects ina disk recording medium, an optical disk device recording data on theoptical disk using such a defect management method, and an optical diskcapable of storing information concerning a defect criteria used forreplacing a defective area of disk with a non-defective area.

[0002] A very high degree of reliability less than 10⁻¹² at worst isrequired of a disk used for recording computer data. Defect-managingsystems have been used hitherto to accommodate the reality that defectsin recording sectors which lead to an error are unavoidable, even veryrare, in the current disk-manufacturing technique.

[0003] Disk mediums are subjected to the defect management for assuringdata reliability even when dirt, scratches or degradation due torepetition of rewriting operation is caused. Primary defects occurringat the time of manufacture of the disks are found through a certifyingprocess carried out at the time of initializing disks, and secondarydefects occurring after being put to use are found through verificationcarried out at the time of writing, or the like. Sectors found to have adefect are replaced, using sectors located in a spare area formed onpart of a disk other than a user area. In the defect management, a pairof a user area and a spare area is called a group.

[0004] In an example of arrangement of user areas and spare areas on adisk, the data area consists of a single group. However, there are manyoptical disks in which a data area is divided into a plurality ofgroups. When a defective group is found in a group, it is firstattempted to replace the defective sectors using sectors in a spare areaof the same group. In many cases, an optical disk is configured suchthat a recording capacity of a spare area is several % of that of a userarea. The 90 mm magneto-optic disk standard defined by ECMA-154 orECMA-201, and the DVD-RAM standard defined by ECMA-272 are examples ofsuch configuration.

[0005] Incidentally ECMA is an abbreviation of European ComputerManufacturers Association, DVD is an abbreviation of digital video disk,and RAM is an abbreviation of random-access memory.

[0006] The presence or absence of a defect in a sector can be determinedby an error in an ID signal representing a physical address of thesector, an error in a recorded data signal, or a servo error signal.

[0007] When a plurality of ID's are recorded in the header area for eachsector, if not less than a predetermined number of ID's for each sectorcontain an error, the sector in question is found have a header defect.In DVD-RAM standard for example, each sector is provided with four ID's,and an error can be detected for each ID. Each sector is not found tohave a header defect it has not more than two ID errors: a sector havingthree or more ID errors is found to have a header defect, since itsreliability is low.

[0008] Further, the presence or absence of an error in a recorded datasignal is detected by the use of an error correcting code added thereto.When more than a predetermined number of errors are included per unit ofrecording, the data signal is found to have a data defect. The “unit ofrecording” may be a sector or a block constituted of a plurality ofsectors depending on the span of an error correcting code (ECC).

[0009] In the DVD-RAM standard, data is recorded in sectors on a disk,and is subjected to error-correcting coding in units of 16 sectors,called an ECC block. Data of 32 KB constituting one ECC block isarranged in the form of matrix of 172×192 bytes (or 172 columns×192rows), and Reed-Solomon codes (inner code PI, outer code PO) of 10 bytesand 16 bytes are added in column direction and row direction,respectively, to constitute a product code.

[0010] The inner code PI is disposed so as to be complete within asector. By means of the inner code PI, the number of error bytes in eachrow of the reproduced data can be determined. In accordance with thedetected number of errors, reliability of each row is evaluated, andwhether each sector or each block has a data defect can be determinedbased on the number. For instance, a sector including four or more rowshaving four or more error bytes is found to be have a data defect, or ablock including six or more such rows are found to have a data defect.

[0011] With regard to detection of defects based on a servo errorsignal, when the magnitude of the servo error signal such as a trackingerror signal exceeds a predetermined value that makes it difficult toensure the servo control stability required of data recording, a sectorin question is found to have a servo defect.

[0012] When a sector is found to have a header defect, a data defect ora servo defect, it is found to be defective.

[0013] Generally, in the defect management, two different methods areused for performing replacement of a sector. One is a slip replacement,and the other is a linear replacement.

[0014] The slip replacement is applied to primary defects. If adefective sector is found at the time of certifying a disk, the nextsector is used in place of the defective sector. In a disk drive device,for accessing a sector containing data, a logical address is convertedinto a physical address representing the position of the sector, and asector having ID's representing the physical address is accessed. Whenthe slip replacement has been performed, the physical address numberscorresponding to the logical addresses are shifted, or “slip” by one.

[0015] The slip replacement is carried out within each group. Forinstance, if there occur two slip replacements of m sectors and nsectors in a user area, the end of the user area of the group is shiftedinto the head of the spare area by (m+n) sectors. If such slipreplacements are made, the linking relation between the physicaladdresses and logical addresses is shifted by the number of replacedsectors for all the sectors succeeding the replaced sectors. Primarydefects subjected to the slip replacement are registered in a PDL(Primary Defect List). The list contains the physical addresses ofdefective sectors in each entry.

[0016] Linking the physical addresses with the logical addresses can bemade only when a disk is initialized, and therefore, the slipreplacement is applied to primary defects only.

[0017] The linear replacement is applied to secondary defects. When adefective sector is found, replacement is effected using spare sectorsin a spare area. When an ECC block (formed of 16 sectors) is found tocontain a defective sector, the entire ECC block is replaced with 16sectors in a spare area. There may be a case where a block in a sparearea having replaced another block is subsequently replaced with anotherblock. A substitutive sectors are given the same logical addresses asthe original sectors.

[0018] The linear replacement is effected within the same group first.For instance, when two linear replacements of m blocks and n blocksrespectively occur in a user area, m blocks and n blocks at thebeginning of the unused part of the spare area are used. It may be sodesigned that when the spare area of the same group has been used up thespare area in another group is used. Secondary defects subjected tolinear replacement are registered in an SDL (Secondary Defect List). Thelist contains physical addresses of defective sectors and substitutivesectors in each entry.

[0019] When such a linear replacement has been made, every time anaccess is made using a logical address which designated a substitutivesector, an access to the substitutive sector and subsequent return haveto be made. Therefore, the average data transfer rate is substantiallylowered when the secondary defects exist.

[0020] A set of the defect lists PDL and SDL is stored in a defectmanagement area within a control information area in each of outer andinner periphery parts. They are disposed at a plurality of locations,and they are recorded together with information on the structure of adisk.

[0021] Generally, in recording devices, criteria for detecting primaryand secondary defects are set in the following way.

[0022] A disk is at its best condition when primary defects are detectedand registered. The number of defects on the disk increases with time orusage due to scratches and dirt, and resultant degradation. Therefore,the primary defects are detected and replacement is effected by using acriteria which is more strict than that for detecting the secondarydefects, so that some additional scratches or dirt will not results inthe finding of a defect according to the criteria for detecting thesecondary defects.

[0023] Although the secondary defects are detected with a criteria whichis less strict than that for the primary defects, a margin of safety isleft between the criteria for detecting the secondary defects and theerror-correcting capability, so as to ensure error correction duringreproduction. In this way, different criteria are used for the primarydefect detection and the secondary defect detection.

[0024] Conventionally, optical disks are used mainly for computer daterecording, and therefore, the primary concern was to improve the datareliability, and defect management mainly consisting of replacementusing spare sectors has been developed to deal with the defects in therecording sectors causing the errors.

[0025] In recent years, with increasing capacity of optical disks, theiruses are expanding to the video recording field, such as in DVD.

[0026] Data files for recording computer data (PC files) are expected tobe completely error-free, and high reliability is required of recording.In contrast, data files for recording audio or vide data (AV files)require recording data inputted continuously in real time. In somecases, errors are permissible as long as the disturbance of reproducedimages or sounds is not noticed, so that data reliability is notrequired to be as high as in computer data recording. Instead,non-interruption of recording is important.

[0027] That is to say, with regard to storage devices for computer datarecording, primary importance is the reliability rather than recordingtime, while, for storage devices for video recording, primary importanceis continuous recording performance. Consequently, in case of using thesame type of disk for recording both audio or video data and computerdata, it is required to ensure reliability and recording speed whichmeet the requirements of the respective recordings. Likewise, defectmanagement is required to be adaptable to both types of recording.

[0028] Conventional defect management for optical disks has thefollowing drawbacks.

[0029] For carrying out replacement to deal with secondary defects of adisk at the time of recording, data is reproduced from the recorded partfor verification, and if errors of more than a prescribed criteria, or adefective part from which reproduction is impossible is found, the datarecorded in that part is re-recorded in substitutive sectors in a sparearea, and data is again reproduced from the substitutive sectors forverification. Thus, when a secondary defect is detected, and replacementis effected, the time needed is four times more of the time needed forrecording data once. In case of recording audio or video data in realtime, it is likely that recording is interrupted if a defect isdetected.

[0030] One solution to this problem is not to detect secondary defectsduring the recording audio or video data. In this case, the reproducedimage or the like may have disturbances at parts having the secondarydefects, but they are considered less objectionable than interruption ofrecording. The underlying assumption is that once primary defects havebeen removed at the time of initialization of the disk, any secondarydefects that might occur will be minor. If the scale of the secondarydefects are beyond the prediction, the disturbance of the reproducedpicture may be intolerable, and thus this solution fails.

[0031] Where the optical disks are used for recording audio or videodata, it is considered unnecessary to detect defects with criteria whichis as strict as that used in recording computer data. This is because,if the excessively strict criteria is used, sectors which arepermissible for audio or video data are also found defective, and videorecording is interrupted when the time-consuming replacement iseffected. Because the conventional defect management method does nottake into consideration the intended use of the optical disk, and thecriteria used is of the same level regardless of the intended use of theoptical disk, and there was no conception of using the optimum defectdetecting method.

SUMMARY OF THE INVENTION

[0032] The present invention has been made overcome the above-outlinedproblem, and its object is to adapt defect management to the type ofdata recorded on an optical disk, or the intended use of the disk.

[0033] Another object is to improve the interchangeability of theoptical disk.

[0034] A further object is to improve the utility of optical disks forrecording audio or video data.

[0035] According to a first aspect of the invention, there is provided amethod of managing defects on an optical disk used for recording data,comprising the steps of

[0036] determining a criteria for detecting said defects according tothe type of data for which defects are to be detected; and

[0037] detecting said defects using said criteria when data is recordedon or reproduced from said disk.

[0038] With the above arrangement, it is possible to use the criteriasuitable for the particular type of data for which said defects are tobe detected.

[0039] Said step of detecting said defects may be performed with regardto data recorded on the disk.

[0040] In this case the defects may be detected when the data isrecorded on the disk, or when the data is reproduced for verification ofthe data having been recorded. When the defects are detected when thedata is recorded, determination of presence or absence of servo defectsand header defects can be made, but determination of presence or absenceof data defects cannot be made. When the defects are detected duringreproduction for verification, presence of absence of data defects aswell as servo defects and header defects can be determined.

[0041] Said step of detecting said defects may alternatively beperformed when the data is reproduced. In such a case, if defects aredetected, the reproduction of the data is re-tried. Decision on whetherthe reproduction is to be re-tried is made using different criteriadepending on the type of data being reproduced.

[0042] The method may further comprise the step of using non-defectiveareas of the optical disk in place of defective areas of the opticaldisk.

[0043] With the above arrangement, the result of the defect detectioncan be used in making a decision as to whether the areas found to bedefective should be replaced with non-defective areas.

[0044] Said step of determining a criteria may include:

[0045] providing a plurality of criteria; and

[0046] selecting one of said plurality of criteria according to the typeof data for which defects are to be detected.

[0047] With the above arrangement, the defect criteria can be determinedsimply by providing a signal which selects one of the plurality ofcriteria provided in advance, rather than specifying the values formingthe criteria.

[0048] Said plurality of criteria may include at least a first criteria,and a second criteria, said second criteria being less strict than saidfirst criteria, and said step of selecting may comprise selecting saidfirst criteria when the data for which defects are to be detected is onefor which time restriction with regard to data recording or reproductionis less strict, and selecting said second criteria when the data forwhich defects are to be detected is one for which time restriction withregard to data recording or reproduction is more strict.

[0049] An example of the data for which time restriction with regard todata recording or reproduction is less strict is computer data. Anexample of the data for which time restriction with regard to datarecording or reproduction is more strict is audio or video data.

[0050] By using a less strict criteria for the audio or video data,interruption of the audio or video data recording is avoided unless thedefect is of such a degree that the resultant disturbance in the soundor picture is intorerable.

[0051] The method may further comprise the step of sending controlinformation for specifying said criteria, from means for processing datato be recorded, to means for recording said data.

[0052] The above-mentioned means for processing data to be recorded isfor example a host device. The above mentioned means for recording thedata is for example a disk device.

[0053] With the above configuration, the host device can set criteriawhich is finely optimized for the type of the data to be recorded on thedisk.

[0054] The data may be recorded in units of recording, and said step ofsending control information may send the control information for eacheach unit of recording.

[0055] With the above configuration, it is possible to dynamically setcriteria which is finely optimized for each unit of recording (e.g.,sector or ECC block), depending on the type of the data to be recordedin each unit of recording. That is, even when different types of data,e.g., audio or video data, and computer data, are both recorded on thesame disk, since the host device sends the criteria control informationin association with the data to be recorded, and the defect managementcan be effected using the optimum criteria for the respective data.

[0056] Said control information specifying the criteria may select oneof a plurality of criteria.

[0057] With the above configuration, the amount of control informationis small, since it only needs to specify one of the plurality ofpredetermined criteria, rather than specifying values forming thecriteria itself.

[0058] Data may be recorded in units of recording, and said method mayfurther comprise the step of recording control information representingthe criteria for each unit of recording, on the optical disk, inassociation with said each unit of recording.

[0059] With the above configuration, the criteria to be used for defectdetection for each unit of recording (sector or ECC block) is known byreading the control information, and can be used for performingmaintenance of the data recorded on the disk.

[0060] According to a second aspect of the invention, there is provideda disk device for accessing data on an optical disk, comprising:

[0061] means for determining a criteria for detecting said defectsaccording to the type of data for which defects are to be recorded; and

[0062] means for detecting said defects using said criteria when data isrecorded on or reproduced from said disk.

[0063] With the above arrangement, it is possible to use the criteriasuitable for the particular type of data for which defects are to berecorded.

[0064] Said detecting means may detect said defects with regard to datarecorded on the disk.

[0065] In this case the defects may be detected when the data isrecorded on the disk, or when the data is reproduced for verification ofthe data having been recorded. When the defects are detected as the datais recorded, servo defects and header defects can be detected, but datadefects cannot be detected. When the defects are detected duringreproduction for verification, data defects as well as servo defects andheader defects can be detected.

[0066] The detecting means may alternatively detect defects when thedata is reproduced. In such a case, if defects are detected, thereproduction of the data is re-tried. Decision on whether thereproduction is to be re-tried is made using different criteriadepending on the type of data being reproduced.

[0067] Said device may comprise means for managing defects on theoptical disk by using non-defective areas of the optical disk in placeof defective areas.

[0068] With the above arrangement, the result of the defect detectioncan be used in making a decision as to whether the areas found to bedefective should be replaced with non-defective areas.

[0069] Said determining means may comprise:

[0070] means for storing a plurality of criteria; and

[0071] means for selecting one of said plurality of criteria accordingto the type of data for which defects are to be detected.

[0072] With the above arrangement, the defect criteria can be determinedsimply by applying a signal for selecting one of the plurality ofcriteria provided in advance, rather than specifying the values formingthe criteria.

[0073] Said plurality of criteria may include at least a first criteria,and a second criteria, said second criteria being less strict than saidfirst criteria, and said selecting means may select said first criteriawhen the data for which defects are to be detected is one for which timerestriction with regard to data recording or reproduction is lessstrict, and selects said second criteria when the data for which defectsare to be recorded is one for which time restriction with regard to datarecording or reproduction is more strict.

[0074] An example of the data for which time restriction with regard todata recording or reproduction is less strict is computer data. Anexample of the data for which time restriction with regard to datarecording or reproduction is more strict is audio or video data.

[0075] By using a less strict criteria for the audio or video data,interruption of the audio or video data recording is avoided unless thedefect is of such a degree that the resultant sound or picture isintolerable.

[0076] Said determining means may determine the criteria according acontrol signal supplied from outside of the device.

[0077] The control signal may be supplied from a host device connectedto the disk device.

[0078] With the above configuration, the host device can set criteriawhich is finely optimized for the type or contents of the data for whichdefects are to be detected.

[0079] The device may further comprise means for recording data, inunits of recording, on the disk,

[0080] wherein

[0081] said determining means may determine the criteria for each ofsaid units of recording, and

[0082] said recording means may also record criteria control informationcontrolling the criteria for each unit of recording, in association withsaid each unit of recording.

[0083] With the above configuration, the criteria to be used for defectdetection for the data of each unit of recording (e.g., sector or ECCblock) is known by reading the control information, and can be used forperforming maintenance of the data recorded on the disk.

[0084] According to a third aspect of the invention, there is providedan optical disk for recording data, comprising an area storing criteriacontrol information specifying criteria to be used for detecting defectsfor data recorded on or reproduced from the disk.

[0085] With the above configuration, the criteria to be used fordetecting defects when the disk is accessed is known by reading thecriteria control information recorded on the disk. Accordingly, themaintenance of the data on the disk is facilitated, and theinterchangeability of the disk is improved since the criteria controlinformation can be read by any disk device.

[0086] Said data may be recorded in units of recording, and saidcriteria control information indicating the criteria to be used fordetecting detect with regard to said each unit of recording may berecorded in association with said each unit of recording.

[0087] With the above configuration, the criteria to be used for eachunit of recording, e.g., sector or ECC block, is known by reading thecriteria control information, and can be used for performing maintenanceof the data recorded on the disk.

[0088] Said information may select said criteria from a plurality ofpredetermined criteria.

[0089] With this configuration, the amount of control information issmall, since it only needs to specify one of the plurality ofpredetermined criteria, rather than specifying values forming thecriteria itself.

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] In the accompanying drawings:

[0091]FIG. 1 is a block diagram of an optical disk device of anembodiment of the present invention;

[0092]FIG. 2 is a block diagram of a defect determining means used inthe optical disk device of FIG. 1;

[0093]FIG. 3A is a schematic diagram showing examples of deformation ofa groove forming a track;

[0094]FIG. 3B is a time chart showing a tracking signal obtained whenthe light spot follows the track shown in FIG. 3A;

[0095]FIG. 4A is a diagram showing the configuration of a sector on aDVD-RAM;

[0096]FIG. 4B is a schematic diagram showing the signal obtained whenthe light spot follows the sector shown in FIG. 4A;

[0097]FIG. 5 is a diagram showing an example of errors in an errorcorrecting block;

[0098]FIG. 6 is a table summarizing two sets of defect criteria;

[0099]FIG. 7 is a table summarizing three sets of defect criteria;

[0100]FIG. 8 is a block diagram of a defect determining means of anotherembodiment;

[0101]FIG. 9 is a diagram showing an example of procedure followed forsetting defect criteria;

[0102]FIG. 10 is a diagram showing another example of procedure followedfor setting defect criteria;

[0103]FIG. 11 is a diagram showing the configuration of an example ofdefect criteria control information; and

[0104]FIG. 12 is a view showing arrangement of information forcontrolling defect criteria on an optical disk.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0105] Embodiments of the invention will now be described with referenceto the attached drawings, in which like parts are indicated by likereference characters.

[0106]FIG. 1 is a block diagram of an optical disk device used toimplement the defect management method according to the invention. Adisk rotating means 4 controls rotation of an optical disk 2 forrecording and reproducing data. An optical head servo means 22 performsposition control over an optical head 6 such that a light spot formed bya light beam focused by the optical head 6 follows the track on the disk2.

[0107] The light reflected from the optical disk 2 representing the datarecorded on the disk 2 is converted in the optical head 6 into anelectrical signal, which is supplied to an address reproducing means 8and a signal reproducing means 10. Based on an ID signal in the header,the address reproducing means 8 reproduces the address of a sectorcurrently accessed. The detected address is sent to a drive controlmeans 14. The signal reproducing means 10 reproduces signals from thesignals supplied from the optical head 6 in accordance with therecording format. A data reproducing means 16 corrects errors in thereproduced signals to produce information, and outputs information to ahost device (not shown) as reproduced data of the desired logical block.

[0108] At that moment, the data reproducing means 16 can recognize asector in which the required data is recorded on the basis of controlsignals received from the drive control means 14. Concurrently, thedrive control means 14 sends a command to control the rotational speedof the disk 2, to the disk rotating means 4. Further, the drive controlmeans 14 determines the position on the disk, of the sector containingthe information to be reproduced, and sends commands to the optical headaccess means 20 for moving the optical head 6 to the position of thesector. The drive control means 14 also sends commands to control theoperation of the servo system. The optical head access means 20 and theoptical head servo means 22 control the position of the optical head 6in accordance with the received commands.

[0109] A defect management control information detecting means 18 readscontrol information necessary for performing defect management, from thereproduced data, and obtains information concerning defect managementsuch as defect management method applied to the disk, arrangement ofspare areas and user areas, status of use of substitutive sectors, anddefect criteria. The information thus obtained is sent to the drivecontrol means 14 and used for controlling devices engaged in defectmanagement at the time of recording or reproducing data.

[0110] Incidentally, all the sectors on the disk are numbered withconsecutive addresses from the inner or outer periphery of the disk.However, the addresses of user data recording sectors are notconsecutive. This is because the physical addresses are assigned notonly to the user data recording sectors, but also to sectors in spareareas provided for defect replacement and sectors in guard areas at zoneboundaries in the case of a zone format disk.

[0111] At the time of performing access from the host device through aninterface, logical block numbers of a file system are used. Therefore,the disk device needs to perform conversion between a logical blocknumber and a sector address. The conversion is carried out by the drivecontrol means 14 in accordance with received information on defectmanagement.

[0112] In writing operation, data sent from the host device is firstinputted to a data recording means 24. The data recording means 24performs error correction coding on the data in accordance with aformat, and outputs the data as signals to be recorded, with timingscontrolled in accordance with the sector addresses on the disk, havingbeen detected by the control signals supplied from the drive controlmeans 14.

[0113] A signal recording means 26 modulates the received signals inaccordance with a recording format and sends them to the optical head 6.

[0114] The optical head 6 writes the signals into the optical disk 2 bydriving a laser.

[0115] At this moment, the optical head 6 is controlled such that alight spot traces the sector the data is to be recorded, by means of theoptical head access means 20 and the optical head servo means 22.

[0116] The drive control means 14 stores defect management controlinformation detected by the defect management control informationdetecting means 18 at the time of disk loading. The logical block numberof the block to be accessed is given by an interface control signalsupplied from the host device, not shown. To be more specific, the hostdevice sends a recording command specifying the logical block number ofthe block where the data is to be written, and the like, to the diskdevice, together with the data to be recorded, or sends a reproducingcommand specifying the logical block number of the block from which thedata is to be read and the like, to the disk device.

[0117] The drive control means 14 converts the logical block number ofthe block to be accessed, to physical addresses, using defect managementinformation, and sends a command specifying the physical addresses ofthe sectors to be accessed, to the optical head access means 20 and datarecording means 24 or data reproducing means 16. The physical addressesof the sectors currently accessed are reproduced by the addressreproducing means 8, and inputted to the drive control means 14. Drivecontrol operations such as control over the optical head access means 20and data recording means 24 or data reproducing means 16 are performedon the basis of the detected current address and the target address.

[0118] A defect determining means 12 makes judgment as to whether asector is defective and is to be replaced. The defect determining means12 receives information necessary for defect determination on eachsector from the optical head servo means 22, address reproducing means8, and data reproducing means 16, and determines presence or absence ofa defect in accordance with a defect criteria set by the drive controlmeans 14, and reports the results of the determination to the drivecontrol means 14. When the sector having been accessed is determined asa defective sector, the drive control means 14 performs the necessaryprocesses. During recording, the drive control means 14 interrupts therecording operation and causes the data of the block to be re-recordedin substitutive sectors. During verifying reproduction, the drivecontrol means 14 causes the data of the block having been recorded, tobe re-recorded in substitutive sectors. During reproduction, the drivecontrol means 14 causes the reproduction to be re-tried. Theseoperations are pre-programmed into the drive control means 14.

[0119]FIG. 2 shows the configuration of the defect determining means 12.It receives servo error signals such as a tracking error signal and afocus error signal from the optical head servo means 22. It alsoreceives a header error signal representing the number of errors in ID'sreproduced for each sector, from the address reproducing means 8. Italso receives a data error signal representing the number of errors inthe reproduced data from the data reproducing means 16.

[0120] In this embodiment, the defect determining means 12 includes twodefect criteria storing means 34 and 36 for storing different defectcriteria A and B, respectively. The two defect criteria A and B areinputted to a defect criteria selecting means 38, which selects andoutputs either one of the two criteria A and B in accordance with adefect criteria setting signal CS. There are three outputs, Rs, Rd, andRh. A reference signal Rs for detecting a servo defect is inputted to aservo defect detecting means 28, a reference signal Rh for detecting aheader defect is inputted to a header defect detecting means 32, and areference signal Rd for detecting a data defect is inputted to a datadefect detecting means 30. They are compared with a servo error signalEs, a header error signal Eh, and a data error signal Ed in therespective defect detecting means 28, 32 and 30, to detect presence orabsence of a servo defect, a header defect, and a data defect. A defectdetecting means 40 receives the outputs of the defect detecting means28, 32 and 30, and outputs a defect detection signal DF when at leastone of the defects has been detected.

[0121] Referring to FIG. 3A and FIG. 3B, detection of a servo defectwill be described. For recording data, a track which has a substantiallyuniform width Wt (the track is actually circular or spiral, but theshort part of the track illustrated can be treated as straight) is used.The track is formed of a continuous guide groove or the like.Consideration will be given to the case where the track is deformed atpoints X and Y. Such deformation may be caused due to dirt introducedduring fabrication of a master disk or a substrate, irregular operationof a manufacturing machine, unevenness of a formed substrate, and otherminor irregularities. Tracking control is performed such that a lightspot follows the centerline 42 c of the track shown by a chain line inFIG. 3A, and a tracking error signal Et shown in FIG. 3B is obtained.The tracking error signal Et is zero when the light spot is followingthe centerline 42 c of the track. When the light spot deviates from thecenterline 42 c, the tracking error signal Et deflects either positivelyor negatively depending on the direction and the amount of deviation.Where there is a deformation of the track and the centerline 42 c of thetrack is bent abruptly, since the light spot cannot follow the abruptbending, the light spot deviates from the centerline 42 c.

[0122] At point X, there is a deflection in the tracking error signal Etdue to the deformation of the track. At point Y, there is also adeflection in the tracking error signal Et due to meander of the track.If the tracking error tolerance limit Rtb shown by the broken line inFIG. 3B is given as a reference for determining a servo defect, a servodefect is recognized at point Y. If a more strict tracking errortolerance limit Rta shown by the chain line in the figure is given,servo defects are recognized both at points X and Y.

[0123] The tracking error tolerance limit Rta corresponds to the valueof the tracking signal Et when the deviation of the light spot isone-fourth the tracking width Wt, and the tracking error tolerance limitRtb corresponds to the value of the tracking signal Et when thedeviation of the light spot is one-eighth the tracking width Wt.

[0124] For instance, if the level Rta at the chain line is used as thedefect criteria A, and the level Rtb at the broken line the figure isgiven as the defect criteria B, it is possible to perform servo defectdetermining process at two different levels. Incidentally, the recordingtrack may not be a continuous groove. In a disk, such as a DVD-RAM,where user data recording areas are formed of lands and grooves, and nogroove is formed at the header parts, which are formed of pre-pits only,it is sufficient to perform a servo defect detection only for areaswhere a groove continues.

[0125] Servo defect detection can be performed with regard to a focuserror signal, in the same way as the tracking error signal.

[0126]FIG. 4A shows the configuration of a sector in a groove track in aDVD-RAM, and FIG. 4B shows the waveform of the signal reproduced fromthe sector shown in FIG. 4A. These drawings will be used for describingthe detection of header defect. A recording sector of a DVD-RAM includesa header area having a sector address and the like at the beginning,followed by a data area for recording user data. The header areaincludes four ID's, indicated as ID1 to ID4 each containing addressinformation representing a sector address. In the sector shown in FIG.4A, ID1 and ID2 are displaced one-half the track width Wt toward theouter periphery of the disk, and are shared with a sector in the outeradjacent land track, while ID3 and ID4 are displaced one-half the trackwidth Wt toward the inner periphery of the disk, and are shared with asector in the inner adjacent land track.

[0127] In a land track not shown, ID1 and ID2 are displaced by one-halfthe track width Wt toward the inner periphery of the disk, and areshared with a sector in the inner adjacent groove track, and ID3 and ID4are displaced by one-half the track width Wt toward the outer peripheryof the disk, and are shared with a sector in the outer adjacent groovetrack. The waveform of the signal reproduced from the header area andthe data area in a sector in a land track is also shown in FIG. 4B.

[0128] The data area following the header is in a groove or a land, andcontains a synchronous signal (SYNC), control information (CI), userdata, and an error-correcting codes, and a buffer, which are recordedsuccessively in this order. The control information CI consists of asmall amount of information (such as the data number of the sector),other than user data.

[0129] The size of user data, together with the control information, inone sector is 2 KB (kilobytes), and error-correcting coding is performedtaking the user data and the control information of 32 KB in 16successive sectors, as a unit, wherein error-correcting codes are addedto the to form an ECC block.

[0130] The error-correcting codes are distributed over the 16 sectors.

[0131] The sector address can be obtained if even one of the four ID'sin a header is read correctly. In criteria B, if none of the four ID'sis read correctly, the sector is found have a header defect, and if twoor more sectors within an ECC block are found to have a header defect,the ECC block is found to have a header defect. In criteria A, if notmore than one of the four ID's is read correctly, the sector is foundhave a header defect, and if one or more sectors within an ECC block arefound to have a header defect, the ECC block is found to have a headerdefect.

[0132] A sector found to be non-defective according to criteria A has atleast two correctly readable ID's. This make it more likely that atleast one ID will remain correctly readable even if the disk is latersoiled or degraded, or transferred to another disk device.

[0133] In this way, it is possible to perform header defectdetermination with two different levels.

[0134]FIG. 5 shows the structure of an ECC block in a DVD-RAM. Thisdrawing is used to describe the data defect detection. In the datarecording means 24, the 23 KB data for 16 sectors are arranged in theform of matrix of 172 bytes in the row direction by 192 bytes in thecolumn direction. A 16-byte parity outer code PO in the column directionis added to each column, and then 10-byte parity inner code PI in therow direction is added to each row.

[0135] Thus, a product code, which is a Reed-Solomon code, of 182bytes×208 bytes is formed.

[0136] When the data is recorded on the optical disk 2, the PO rows areinterleaved with the other rows so that the error-correcting code bytesare evenly distributed over all 16 sectors of the ECC block.

[0137] At the time of reproduction, the data reproducing means 16rearranges the reproduced signal into a matrix of 182 bytes×208 bytes,and first detect and correct any errors of each row by means of the10-byte inner code PI. The inner code PI is capable of correcting errorsin up to five bytes per row, and detecting errors in up to ten bytes perrow.

[0138] Next the 16-byte outer code PO is used to detect and correct anyremaining errors. The outer code PO is capable of correcting errors inup to 8 bytes per column, and detecting errors in up to 16 bytes percolumn. These error detecting and correcting capabilities can beimproved by repeating the PI-PO error correction process, although theadditional repetitions require additional circuitry and additional time.

[0139] When a large number of errors are detected and corrected, itbecomes likely that some of the corrections are wrong, the correcteddata differing from the original data. Criteria A and B are thereforeset, for example, as follows. In criteria A, a row is considered to havea data defect if errors are detected in at least four bytes, which isclose to the error-correcting limit of the PI code, and an ECC block isconsidered to have a data defect if it has at least eight rows having adata defect. In less strict criteria B, a row is considered to have adata defect if errors are detected in at least eight bytes, which isclose to the repeated error-correcting limit of the PI code, and an ECCblock is considered defective if it has at least eight rows having adata defect. When an ECC block is considered to have a data defect, allsixteen of its constituent sectors are replaced.

[0140] In this way, it is possible to perform data defect determinationwith two different levels.

[0141] In FIG. 5, row three has errors in four bytes, indicated by x's.This row is deemed to have a data defect under criteria A, but not undercriteria B.

[0142] In this way, the presence or absence of defect in each sector canbe determined with respect to each of the servo defect, the headerdefect, and the data defect, according to the defect criteria suppliedto each defect detecting means. FIG. 6 summarizes the defect criteria Aand B described above described as examples for the respective defects.The set of criteria A are stored in the criteria storing means 34, whilethe set of criteria B are stored in the criteria storing means 36. It isthen possible to switch between the two levels of criteria A and B bymeans of the criteria selecting means 38, according to the criteriasetting signal CS.

[0143] In the case of recording computer data, a high reliability isrequired so that the data once recorded are not lost or changed. Forthis reason, verifying reproduction is often effected at the time ofrecording. Accordingly, during recording and during verificationproduction, the strict criteria A is applied to ensure that the correctdata is recorded.

[0144] In contrast, in the case of audio or video data, continuousrecording at a high transfer rate is required. Accordingly, verifyingreproduction is often omitted, ignoring data defects. Even if somedefects occur during recording, as long as occurrence of the defects isof such a degree that the defects can be corrected or concealed later atthe time of reproduction, it is preferable to continue recordingoperation ignoring the defects, since it will improve the performanceand the operability as a recorder. For this reason, the criteria set forservo defects and header defects are set at a less strict level at whichthe recorded data can be corrected or concealed.

[0145] When the two different defect criteria A and B available, thestrict criteria A is used for recording computer data, while the lessstrict criteria B is used for recording audio or video data.

[0146] There are situations where more than two different levels ofreliability are required depending on types of data to be recorded. Forinstance, there is a situation where three different levels arerequired, one for recording computer data, another for recordingimportant audio or video data, and the last one for recording normalaudio or video data. In such a situation, as shown in FIG. 7, provisionis made to enable switching among three different defect criteria A, B,and C. Criteria A and B are the same as those described with referenceto FIG. 6, and are used for recording computer data and for recordingnormal audio or video data, respectively.

[0147] The criteria C is used for recording important audio or videodata, and therefore, it has strictness intermediate between the criteriaA and B. In the criteria C, the allowable deviation in tracking error isone-sixth the track width Wt, and an ECC block is found to have a headerdefect if all four ID's are unreadable in any one sector. Regarding datadefects, criteria C and A are the same.

[0148] To use the three different sets of defect criteria, the defectdetermining means 12 should have an additional criteria storing means,in addition to the members shown in FIG. 2, and the criteria selectingmeans 38 should be able to select among the criteria A, B and C suppliedfrom the above-mentioned additional criteria storing means, as well asthe criteria storing means 34 and 36 in FIG. 2, in accordance with thecriteria setting signal CS.

[0149]FIG. 8 shows another embodiment of the defect determining means12. The configuration of FIG. 8 is different from the configuration ofFIG. 2 in that the criteria storing means 34 and 36, and the criteriaselecting means 38 which makes selection according to the criteriaselecting signal CS shown in FIG. 2 are replaced with a defect settingand storing means 46 which makes setting according to the criteriaselecting signal CS.

[0150] The defect criteria to be applied is supplied from a host device(not shown) through an interface to the drive control means 14. Inresponse, the drive control means 14 generates a criteria setting signalCS specifying the criteria.

[0151] In the defect determining means 12 of FIG. 2, the defect criteriastored in the respective criteria storing means are fixed. However, inpractical use, it may be desirable that the host device which controlsthe disk device (recording device) can flexibly vary the criteria so asto optimize the reliability and the transfer rate, depending on thenature, type, characteristics, and the degree of importance of the datato be recorded. For instance, a countermeasure for errors may beprovided in the application software or file system. That is, errorcorrecting coding may be applied before transmitting the data to thedisk device at a predetermined rate. In this case, the defect managementat the disk device is not so important, and the capability of continuousreal-time recording at a high data transfer rate may be important.

[0152] The embodiment described above can meet with these requirements.

[0153] An embodiment of procedure followed in setting a defect criteriawill be described with reference to FIG. 9. First, the host device setsthe defect criteria to be used, according to type or contents of thedata to be recorded. Then, a command for setting the criteria is sentfrom the host device to the disk device (drive). The disk device selectsor sets the criteria upon reception of the command accordingly. In thesystem shown in FIG. 2, the command sent from the host device to thedisk device is one for merely specifying selection between the criteriaA and B. In the system shown in FIG. 8 in which the defect criteria canbe set, the system is so configured that the defect criteria can be setarbitrarily at the host device, and the command indicates the defectcriteria set at the host device. Details of the command for setting thedefect criteria may be one which will be described later with referenceto FIG. 11, in which the defect criteria control information can selectone among a plurality of criteria independently, for each of the servodefect, header defect, and data defect.

[0154] The host device then sends a recording command together with thedata to be recorded. Upon reception of the command, the disk devicerecords data in the specified sectors, and performs the defectmanagement using the defect criteria set in the manner described above,and reports the results of the defect management to the host device. Thehost device terminates a series of recording when it confirms thatrecording has been completed correctly. If the recording has been doneincorrectly, a predetermined process (re-writing or informing the user)for dealing with the incorrectness is carried out.

[0155] According to the procedure of FIG. 9, the host device, whichknows the contents of the data to be recorded, sets the defect criteriafinely optimized according to the type or contents of the data. It istherefore possible to provide flexibility for obtaining an optimumcombination of reliability and transfer rate according to the intendeduse of the data.

[0156]FIG. 10 shows another embodiment of a procedure followed forsetting a defect criteria. In this embodiment, a command which sets adefect criteria and also instructs data recording is sent. First, thehost device determines a defect criteria to be used in accordance withthe type or contents of the data to be recorded, and then prepares thedata to be recorded. This order may be reversed.

[0157] Then, the host device sends the recording command which also setsthe defect criteria, to the disk device. In accordance with thedesignated defect criteria, the disk device selects or sets thecriteria. The designation of the setting sent from the host device tothe disk device may be one for specifying selection among a plurality ofpreset criteria (such as between the criteria A and B), or one forsetting an arbitrary criteria.

[0158] The disk device records the data received together with thecommand, on the disk, while performing defect management in accordancewith the defect criteria which has been set as described above, andinforms the host device of the result. According to this embodiment, itis possible to obtain an optimum combination of reliability and transferrate depending on the intended use of the disk, as in other embodimentsdescribed earlier. Moreover, because the number of commands transferredis reduced, the overhead is reduced, and the possibility of the transferrate becoming lowered is reduced.

[0159] A manner of recording control information representing the defectcriteria designated at the time of data recording, in every sector on adisk will now be described. FIG. 11 shows the configuration of a defectcriteria control information. With this configuration, one of fourdifferent criteria can be specified for each of the servo defect, theheader defect and the data defect independently, by using one byte.

[0160] The most-significant bit b7 indicates the mode of designation ofthe defect criteria. If the value of bit b7 is “1”, the mode designatedby other bits of the control information byte is used, while if thevalue is “0” the default criteria which the disk device has is usedignoring the other bits of the control information byte.

[0161] The next bit b6 indicates the range within which the defectcriteria should be applied. If the value of bit b6 is “1”, the mode setby other bits in the control information byte of are applied for eachunit of recording, e.g., each sector or block. If the value of bit b6 is“0” the same criteria is to be applied over the entire surface of thedisk.

[0162] The next two bits (b5 and b4) indicate the criteria applied forthe servo defect, among the four criteria. If the combined value of bitsb5 and b4 are “11” the tracking error tolerance above which the servodefect is recognized is one-forth the track width Wt. If the combinedvalue is “10” the tolerance is one-sixth the track width Wt. If thecombined value is “01” the tolerance is one-eighth the track width Wt.If the combined value is “00” the tolerance is one-tenth the track widthWt.

[0163] The next two bits b3 and b2 indicate the defect criteria to beapplied for the header defect, among the four criteria. If the combinedvalue of the bits b3 and b2 is “11” the ECC block is found to have aheader defect if all four ID's are unreadable at two or more of itssectors. If the combined value is “10” the ECC block is found to have aheader defect if three or more ID's are unreadable at two or more of itssectors. If the combined value is “01” the ECC block is found to have aheader defect if all four ID's are unreadable at one or more of itssectors. If the combined value is “00” the ECC block is found to have aheader defect if three or more ID's are unreadable at one or more of itssectors.

[0164] The last two bits b1 and b0 indicate the defect criteria to beapplied for the data defect, among the four criteria. If the combinedvalue of the bits b1 and b0 is “11”, the ECC block is found to have adata defect if at least 16 of its rows have errors in at least 8 byteseach. If the combined value is “10”, the ECC block is found to have adata defect if at least 8 of its rows have errors in at least 8 byteseach. If the combined value is “01”, the ECC block is found to have adata defect if at least 8 of its rows have errors in at least 4 byteseach. If the combined value “00”, the ECC block is found to have a datadefect if at least 6 of its rows have errors in at least 4 bytes each.

[0165] The above described defect criteria control information can belocated in each sector which constitutes a minimum unit of recording. Ina DVD-RAM, a one-byte area may be reserved in the control informationarea located at the beginning of the data area shown in FIG. 4. Thecriteria may be set for each sector separately. The same defect criteriacontrol information may be set in all the sectors within the same ECCblock, or in predetermined sectors, so that the defect criteria controlinformation is repeatedly recorded, and the range within which the samedefect criteria should be applied may be made to coincide with the unitof error correction (ECC block).

[0166] The provision for enabling setting the finely optimized criteriaimproves the utility for the user in multimedia applications in whichthe audio or video data and computer data are intermixed with eachother. It should be noted that the defect criteria to be applied to therespective data can be switched at the system (host device) depending onthe contents of the data, and it is possible to realize a flexibilityfor obtaining the optimum combination of the reliability and transferrate.

[0167] It is possible to pre-select a defect criteria to be used inrecording on a disk, and record the criteria as defect criteria controlinformation on the disk, before the disk is used. FIG. 12 shows anexample of arrangement of control information areas, and a datarecording region including user areas and spare areas, and arrangementof defect criteria control information in the control areas. The datarecording region is divided into groups, each of which includes a userarea and a spare area. The control information areas are disposed nearthe inner and outer peripheries of the disk, and the same controlinformation is recorded on the respective control information areas.

[0168] In a known example, a defect management method is recorded in acontrol information area. In contrast, according to this embodiment,defect criteria control information is stored in a control informationarea. At the time of starting a disk, the disk device reads the defectcriteria control information to know the defect criteria. If the defectcriteria suitable for the intended use, such as computer data, audio orvideo data, or the like is recorded, the defect determination accordingto the defect criteria can be made.

[0169] If one bit is provided in the control information area forrecording the defect criteria control information, it is possible torecord two sets of defect criteria, and selectively use them. Forrecording three or four sets of defect criteria, and using themselectively, two bits should be provided in the control informationarea. If one byte is provided in the control information area, it ispossible to select one of the criteria for each of the servo defect,data defect and header defect, and to specify a combination of specificdefect criteria for the respective types, as described with reference toFIG. 11.

[0170] With such a provision, if the information is recorded once at thetime of initialization of the disk, the defect criteria can be appliedto all the data thereafter recorded on the disk. It is thereforepossible to eliminate to need to set the defect criteria each time thedata is recorded. Accordingly, the recording can be effected at a highspeed, and in a simple manner.

What is claimed is:
 1. A method of managing defects on an optical diskused for recording data, comprising the steps of determining a criteriafor detecting said defects according to the type of data for whichdefects are to be detected; and detecting said defects using saidcriteria when data is recorded on or reproduced from said disk.
 2. Themethod according to claim 1, wherein said step of detecting said defectsare performed with regard to data recorded on the disk.
 3. The methodaccording to claim 2, wherein said step of detecting said defects isperformed when the data is reproduced for the purpose of verification ofdata having been recorded.
 4. The method according to claim 1, furthercomprising the steps of using non-defective areas of the optical disk inplace of defective areas of the optical disk.
 5. The method according toclaim 1, wherein said step of determining a criteria includes: providinga plurality of criteria; and selecting one of said plurality of criteriaaccording to the type of data for which defects are to be detected. 6.The method according to claim 5, wherein said plurality of criteriainclude at least a first criteria, and a second criteria, said secondcriteria being less strict than said first criteria, said step ofselecting comprises selecting said first criteria when the data forwhich defects are to be detected is one for which time restriction orreproduction with regard to data recording is less strict, and selectingsaid second criteria when the data for which defects are to be detectedis one for which time restriction with regard to data recording orreproduction is more strict.
 7. The method according to claim 2, furthercomprising the step of sending control information for specifying saidcriteria, from means for processing data to be recorded, to means forrecording said data.
 8. The method according to claim 7, wherein data isrecorded in units of recording, said step of sending control informationsends the control information for each each unit of recording.
 9. Themethod according to claim 7, wherein said control information specifyingthe criteria is for selecting one of a plurality of criteria.
 10. Themethod according to claim 2, wherein data is recorded in units ofrecording, and said method further comprises the step of recordingcontrol information representing the criteria for each unit ofrecording, on the optical disk, in association with said each unit ofrecording.
 11. A disk device for accessing data on an optical disk,comprising: means for determining a criteria for detecting said defectsaccording to the type of data for which defects are to be recorded; andmeans for detecting said defects using said criteria when data isrecorded on or reproduced from said disk.
 12. The device according toclaim 11, wherein said detecting means detects said defects with regardto data recorded on the disk.
 13. The device according to claim 11,further comprising means for managing defects on the optical disk byusing non-defective areas of the optical disk in place of defectiveareas.
 14. The device according to claim 11, wherein said determiningmeans comprises: means for storing a plurality of criteria; and meansfor selecting one of said plurality of criteria according to the type ofdata for which defects are to be detected.
 15. The device according toclaim 14, wherein said plurality of criteria include at least a firstcriteria, and a second criteria, said second criteria being less strictthan said first criteria, said selecting means selects said firstcriteria when the data for which defects are to be detected is one forwhich time restriction with regard to data recording or reproduction isless strict, and selects said second criteria when the data for whichdefects are to be recorded is one for which time restriction with regardto data recording or reproduction is more strict.
 16. The deviceaccording to claim 12, said determining means determines the criteriaaccording a control signal supplied from outside of the device.
 17. Thedevice according to claim 12, further comprising means for recordingdata, in units of recording, on the disk, wherein said determining meansdetermines the criteria for each of said units of recording, and saidrecording means also records criteria control information controllingthe criteria for each unit of recording, in association with said eachunit of recording.
 18. An optical disk for recording data, comprising anarea storing criteria control information specifying criteria to be usedfor detecting defects for data recorded on or reproduced from the disk.19. The optical disk of claim 18, wherein said data is recorded in unitsof recording, and said criteria control information indicating thecriteria to be used for detecting detect with regard to said each unitof recording is recorded in association with said each unit ofrecording.
 20. The optical disk of claim 18, wherein said informationselects said criteria from a plurality of predetermined criteria.